The programmable locks of the kind to which applies the present invention and which are described in the cited documents comprise, within a rotor rotatably mounted inside the stator, a number of key followers movable along their longitudinal and transversal directions, intended to cooperate with the codification conformations of a key inserted into the rotor keyhole, and locking pins having movability along their own longitudinal directions, which are the blocking members of the lock. The key followers and the locking pins form pairs each comprising a locking pin and a key follower, and they are provided with toothings intended to mutually cooperate, in different relative positions, for determining the lock codification. A transversally displaceable stop bar, cooperating with a longitudinal stator groove, is susceptible of cooperating with recesses of the locking pins in order to immobilize the locking pins when the rotor is rotated within the stator and, as a consequence, the stop bar comes out of said groove and engages the locking pins. A transversally displaceable change bar is slidably engaged with the key followers and normally retains the key followers engaged with the locking pins, but this change bar, when it enters said stator groove, transversally displaces the key followers by disengaging the same from the locking pins, thus allowing the modification of the lock codification by replacing the former key by a new different key.
A requirement laid down for the known locks of this kind is to ensure that the codification change may be effected only by using a special change key. This gives the security that the lock codification cannot be modified or altered by mistake. Another requirement, common to all kinds of locks, is to allow an increase in the number of different keys that can be provided. Still another requirement common to all kinds of locks is to hinder the non-authorized manufacture of key copies. Several solutions have been proposed for all these problems, but in general they involve complications or constructive difficulties, thus increasing the lock size and cost.